Atomic Structure

Question 1

Relative charge of proton, neutron and electrons

Answer 1

PROTON = +1
NEUTRON = 0
ELECTRON = -1

Question 2

Principles of a Time Of Flight (TOF) mass spectrometer

Answer 2

IONISATION - sample vaporised into a gas form, then put into mass spectrometer and is immediately ionised (by Electrospray OR electron impact).
ACCELERATION - ions accelerated by an electric field, acceleration plate neg. Charged in front to attract ions and pos. Charged on back to repel ions further down spectrometer. Acceleration gives all ions constant kinetic energy
ION DRIFT - electric field absent. Lighter ions drift thru faster.
ION DETECTION - lighter ions detected first, ions are therefore separated based on mass.
DATA ANALYSIS

Question 3

Define first ionisation energy

Answer 3

the energy needed to remove 1 electron from each atom of an element in 1 mole of gaseous atoms, to form 1 mole of gaseous ions with a +1 charge.

Question 4

Electrospray vs Electron Impact ionisation

Answer 4

ELECTROSPRAY = voltage is applied, causing each particle to gain an H+ ion. This converts the sample into a gas made up of positive ions

ELECTRON IMPACT = An electron gun is used to fire high energy electrons at the particles. The electrons repel a single electron out of each particle, causing them to become charged, forming 1+ ions.

Question 5

Relative mass of proton, neutron and electron

Answer 5

Proton = 1
Electron = 1/1860
Neutron = 1

Question 6

explain how first and successive ionisation energies
in Period 3 (Na–Ar) give evidence for electron configuration in sub-shells and in shells.

Answer 6

In period 3 there is a general increase in ionisation energies. However there are some anomalies:

Mg and Al - there is a decrease since the outer electron of Al is in a 3p orbital (a slightly higher energy level) and this requires less energy to remove.

P and S - there is a decrease. In P each of the three 3p orbitals only contains one electron so there is no repulsion. In S one of the 3p orbitals contains 2 electrons so repulsion is present. The repulsion between these paired electrons makes it easier to remove 1 electron although there is an increase in nuclear charge.

Question 7

explain how first and successive ionisation energies
in Group 2 (Be–Ba) give evidence for electron configuration in sub-shells and in shells.

Answer 7

In group 2, there’s a general decrease in 1st IE. This is because the outer electron is in a main energy level that gets futher from the nucleus. As you go down the group the nuclear charges increase. However the electrons are shielded from it so its easier to remove

Question 8

Factors affecting Ionisation Energies

Answer 8

Nuclear charge, shielding, repulsion, distance, atomic radii